# General question about atomic structure

1. May 10, 2012

### Perpendicular

the product of velocity of an electron and the principal quantum number is independent of which variable ?

options given : a) velocity b) principal quantum number c) speed of revolution d ) energy of electron

I wrote c, is it correct ?

2. May 14, 2012

### ptolema

Well, by process of elimination, a) and b) are incorrect because they are clearly variables in the product of electron velocity and principal quantum number. d) is incorrect because the energy of an electron generally increases with the principal quantum number, so changes in electron energy may be indicative of a change in the principal quantum number. So that leaves c). I don't know if this is 100% correct, but this is how I approached it.

3. May 15, 2012

### Perpendicular

well, under the Bohr model , it's B. But I'm not sure if that holds true for other models.

4. May 15, 2012

### stef6987

I'm pretty sure it is B

5. May 16, 2012

### Perpendicular

can you explain how to calculate velocity in a model other than Bohr's ? Say I want to calculate the velocity of an electron in a non-hydrogen like atom - let's say , 4s electron of Calcium. How do I go about it ?

6. May 16, 2012

### Saitama

Which model are you currently studying in your classes?

7. May 16, 2012

### Perpendicular

Bohr + full orbital model w/ pauli exclusion principle and all that, dunno what it's called...

8. May 16, 2012

### Saitama

Since you are studying Bohr model, you should be using this formula for velocity:-
$$v=2.18 * 10^8*\frac{z}{n} m/s$$
(Correct me if i am wrong because i am not sure about the constant value.)
where z is atomic number and n is the principal quantum number.

Now simply do what the question has asked.

9. May 17, 2012

### Perpendicular

10^6 lol. But yeah, you're right.